Phase Transformation and Magnetic Properties of Nanocrystalline Fe73.5CulNb3Si22.5-xBx (x= 6,9) Alloys

The coercivity and phase transformations of Fe73.5Cu 1Nb3Si22.5-xBx nanocrystalline alloys as a function of temperature (540 and 620°C), annealing times (up to 240 min), and composition (x=6 and 9) are investigated by means of magnetic measurements, Mossbauer spectroscopy, and X-ray diffractometry. Nanocrystalline microstructure after annealing at 540°C gives rise to a softening of the material, while, after annealing at 620°C for short times, a magnetic hardening is observed before a significant increase in size of the ?-Fe(Si) grains and the detection of a secondary Fe2B phase. The initial stages of Fe2B precipitation seem to be responsible for this magnetic hardening